Wet grinder

ABSTRACT

The grinder disclosed herein has a modified design of the vanes for mixing the grinding bodies with the material in the course of grinding. Each vane is made in the form of a trough arranged around the shaft with its hollow facing the shaft; the trough is provided with a slot extending throughout the length of the trough bottom. Such an arrangement makes it possible to increase radically the force and number of collisions of the particles with the grinding bodies and with one another, thus improving the grinding efficiency characterized by a better fineness of grind and an increased yield of the main fraction.

United States Patent Soloviev et al.

[ WET GRINDER Filed: May 20, 1971 Appl. No.: 145,303

US. Cl. 241/4615; 241/172; 259/8 Int. B02C 17/16 Field of 241/46 R, 46.15,171, 172,

' References Cited 1 UNITED STATES PATENTS 4/1957 Crawford 259/8 Dec. 23, 1975 Wahl 241/172 X Onishi et al 259/8 [57] ABSTRACT The grinder disclosed herein has a modified design of the vanes for mixing the grinding bodies with the material in the course of grinding. Each vane is made in the form of a trough arranged around the shaft with its hollow facing the shaft; the trough is provided with a slot extending throughout the length of the trough bottom. Such an arrangement makes it possible to increase radically the force and number of collisions of the particles with the grinding bodies and with one another, thus improving the grinding efficiency characterized by a better fineness of grind and an increased yield of the main fraction.

3 Claims, 3 Drawing Figures US Patent Dec.23, 1975 SheetlofZ 3,927,838

US. Patent Dec. 23, 1975 Sheet2 0f2 3,927,838

F/GJ

WET GRINDER The present description relates togrinding equipment and more specifically it relates to wet grinders wherein the material being treated is ground in the course of its mixing it with-grinding bodies such as sand, glass beads, steel shot, etc.

The material and grinding bodies are mixed by mixers consisting of a system of shaft-mounted vanes, each made in the form of a disc, flat ring, auger screw, or of any helical shape (see, for example, US. Pat. No. 2.581.414, Cl. 241-22, and FRG Pat. Nos. 1,211.905, 1.109.988, 1.183.344, 1.507.671 and 1.296.960, C1. 50c 17/20).

Also known in the art are other grinders of the same application wherein the mixer has the form of a cylindrical bucket with a blind bottom, mounted on a shaft (see, for example, FRG Pat. No. 1.198.176 Cl. 50c 17/20).

It is known that the fineness of grind in these grinders is characterized by the size of the particles of the main fraction which is l-2 mm, with the content of this fraction not exceeding 90%. i

An object of the invention is to increase the fineness of grind and the yield of the main fraction.

Another object of the invention is to modify the design of mixer vanes in order to increase considerably the force and frequency of collisions of the particles with the grinding bodies and with one another.

These objects have been accomplished by providing a wet grinder wherein grinding is carried out by grinding bodies in the course of their mixing with the material under treatment by the shaft mounted vanes in which, according to the invention, each vane is made in the form of a trough arranged around the shaft and having a hollow facing the shaft, the bottom of the trough being provided with a slot extending throughout the length of said bottom.

Such a design of the vanes allows the particle to be moved at a speed approaching that of vane rotation and creates the best turbulences inside the grinder, these turbulences increasing radically the number of collisions of the particles with the grinding bodies and with one another.

To increase the speed of the flow discharged from the slot it is practicable that the side walls of the trough should become narrower towards the slot over tapering surfaces thus forming a radial-circular flow restrictor.

For dividing the flow inside the trough into two branches, because the impact of the branching flows discharged from the slot ensures better collision of the particles, the trough has a partition inside, at the slot level, said partition dividing the space inside the trough into upper and lower zones.

To ensure a higher turbulence of the flow which intensifies mixing inside the grinder, it is practicable that the side walls of the trough should be provided with through holes.

Better mixing and distribution of the material along the height (or length) of the grinder will be obtained if the holes in the side walls of each vane are offset relative to the holes in the adjacent vane so as to arrange these holes along helical lines. This provides for the movement of the material from one vane to another.

While handling particularly hard materials, such as some types of pigments, when it becomes necessary to intensify the collisions of the particles with the grinding 2 bodies and with one another, it is practicable that a certain direction be given to the streams leaving the holes in the side walls of the trough. For this purpose said holes are fitted with nozzles at the external side of the trough, said nozzles being directed towards the walls of the grinder. sheel.

Now the invention will be described in detail by way of example with reference to the accompanying drawings in which:

FIG. 1 is a vertical section of the grinder according to the invention (only one vane is shown for convenience);

FIG. 2 is a sectional view of the vane in the form of a trough with tapering side walls whose holes are fitted with built-in nozzles, the trough being provided with a partition (arrows show the direction of suspension carrying the material to be ground and the grinding bodies); 1

FIG. 3 is a sectional view'of another type of vane in the form of a trough with rounded side walls (arrows show the direction of suspension carrying the material to be ground and the grinding bodies).

The grinder is intended for extra-fine grinding of hard materials, both organic and mineral. The grinder comprises a shell 1 (FIG. 1) encased in a cooling water jacket 2, Installed in the shell 1 on bearings 3 is a shaft 4 carrying mixing vanes 5. Each vane is made in the form of a trough (FIGS: L3) arranged around the shaft 4 (FIG. 4) and having a hollow which faces said shaft. The trough bottom has a slot 6 (FIG. l-3) extending throughout its length. The side walls 7 (FIGS. 1 and 2) of the trough become narrower towards the slot over tapering surfaces, thus forming a radial-circular flow restrlctor.

The side walls 7 of each trough have through holes 8; the holes (FIG. I) of one trough are offset relative to the holes 8b, 86, etc. of the adjacent trough so that these holes become arranged along helical lines 9, viewing along the length of the shaft 4, The holes 8 are provided at the end with nozzles 10 (FIGS. 1 and 2) located on the outer side of the trough. The nozzles 10 are directed towards the side walls of the grinder shell 1. Inside of each trough, level with the slot 6, there is a disc-shaped partition 1] which divides the space between the trough and the shaft 4 into the upper and lower zones. The slots 12 and 13 formed between the side walls 7 of the trough and the partition 11 are somewhat larger in width than the grinding bodies.

The trough walls should preferably be of the shape described above, i.e. they must have become narrower over tapering surfaces toward the slot, though the side walls 7a (FIG. 3) can be ofa round or any other shape.

The trough can also be located along a closed or open helical line, performing simultaneously the functions of an auger screw.

In plan view the troughs may be either round or polygonal.

The grinder shell may be either vertical or horizontal.

The material to be ground is fed into the grinder shell 1 in the form of an aqueous or any other suspension from underneath, through pipe connection 14 (FIG. I) fitted with a non-return valve 15.

Owing to the above-described design of the mixing trough-shaped vanes 5 the suspension moves inside the grinder in the directions shown by arrows in FIG. 1.

Owing to rotation of the shaft 4 and vanes 5 the particles and grinding bodies are carried by the liquid streams into the central, more rarefied zone of the grinder working chamber, being then thrown by the centrifugal force to the trough walls 7 (7a) and, rotating with the troughs, acquire a velocity approaching the rotation speed of the vanes 5.

Sliding over the tapering surfaces of the walls 7, the particles of the material are thrown out together with the flow of liquid from slots 6 in a radial-circular stream directed towards the side walls of the shell 1; in the course of this process, the particles collide with the grinding bodies circulating within the space between the vanes and the walls of the shell 1, and with one anohter.

The maximum intensity of collisions is promoted by the additional streams of liquid discharged fanwise from the nozzles 10 and by the collisions of these additional streams with one another and with the streams discharged from the slots 12 and 13. The streams of suspension discharged from the slots 12 and 13 strike the side walls of the shell 1, are reflected from them and sucked back into the central zone of the grinder working chamber. Such circulation of the particles goes on continuously as long as the vanes 5 keep rotat- The helical layout of the holes 8, and, consequently, of the nozzles 10, along the height of the grinder shell I ensures consecutive movement of the particles from one vane 5 to another from bottom up (Care should be taken that rotation of the shaft 4 coincides with the direction of hand of the helical lines 9 along which the holes 8 and nozzles 10 are located).

M the material is gradually ground, it moves to the upper portion of the grinder and is taken out through the discharge chute 16. Solid discs 17 prevent infiltration of air from above.

The flywheel 18 (FIG. 1) stabilizes steddy rotation of the shaft 4. The sieve 19 located in the upper portion of the grinder provides for continuous separation of the grinding bodies from the suspension of the material being ground.

The grinding bodies in such grinders consist of sand, glass beads, steel shot, and other conventional grinding bodies.

The circulation of suspension streams described above which ensures this intensive turbulent diffusion of the vortices around the vanes 5 throughout the volume of the working chamber provides for the maximum intensity of collision of the particles with the grinding bodies and with one another.

As has been proved by experiments, the size of the ground particles of the main fraction obtained in the grinder disclosed herein is not larger than 1 micron while the yield of the main fraction rises to not less than What is claimed is:

1. In a wet grinder the combination of a shell; a chamber formed within said shell and being adapted to receive a quantity of grinding bodies; a rotatable shaft extending through said chamber and a plurality of vanes secured to said shaft in axially spaced relationship, each said vane being trough-shaped and having a bottom and side walls defining interior concave sur' faces, each said trough-shaped vane being disposed about said shaft with its concave surface facing the shaft; the improvement comprising: each said troughshaped vane having a slot extending throuh the entire bottom length thereof, at least one of the side walls of said trough-shaped vane having through apertures; and external nozzles integrally formed with said troughshaped vane, said through apertures communicating with said external nozzles, the nozzles being arranged from one vane to the next so as to aid in moving material being treated up through the grinder chamber.

2. An improvement as claimed in claim I, said side walls of each said trough-shaped vane becoming narrower towards the slot through tapering surfaces forming a radial and peripheral flow restrictor.

3. An improvement as claimed in claim 1, each said trough-shaped vane comprising a partition formed along the plane of said slot and extending transversely relative to said shaft, said partition being coextensive with said slot and dividing the space within said trough. 

1. In a wet grinder the combination of a shell; a chamber formed within said shell and being adapted to receive a quantity of grinding bodies; a rotatable shaft extending through said chamber and a plurality of vanes secured to said shaft in axially spaced relationship, each said vane being trough-shaped and having a bottom and side walls defining interior concave surfaces, each said trough-shaped vane being disposed about said shaft with its concave surface facing the shaft; the improvement comprising: each said trough-shaped vane having a slot extending throuh the entire bottom length thereof, at least one of the side walls of said trough-shaped vane having through apertures; and external nozzles integrally formed with said trough-shaped vane, said through apertures communicating with said external nozzles, the nozzles being arranged from one vane to the next so as to aid in moving material being treated up through the grinder chamber.
 2. An improvement as claimed in claim 1, said side walls of each said trough-shaped vane becoming narrower towards the slot through tapering surfaces forming a radial and peripheral flow restrictor.
 3. An improvemeNt as claimed in claim 1, each said trough-shaped vane comprising a partition formed along the plane of said slot and extending transversely relative to said shaft, said partition being coextensive with said slot and dividing the space within said trough. 